Landscaping, Maintenance
& Retrofit Guidance

Section 1 — Chapter 7

Landscaping and Vegetation Considerations

1.1  Planting Goals

Chapter 7 establishes vegetation as a functional engineering component of stormwater BMPs, not an aesthetic afterthought. Both manual editions define five core planting goals that must be met to ensure long-term performance:

• Pollutant uptake and cycling: Plant root systems and associated soil microbial communities actively uptake and transform nutrients from infiltrating stormwater. Nitrogen and phosphorus are stored in above-ground biomass and cycled through decomposition or harvest.
• Hydrologic performance: Vegetation drives evapotranspiration (ET), contributing to volumetric reduction and restoring available storage between storm events. Deep-rooted native species maintain soil macroporosity and prevent compaction that degrades infiltration rates over time.
• Erosion control and structural stability: Root systems bind soil within and around BMPs, preventing surface erosion during storm events and stabilizing inlet/outlet areas and side slopes.
• Sediment trapping: Dense vegetation in inflow zones and forebays reduces stormwater velocity, causing suspended sediment to settle in the pretreatment area rather than entering the primary BMP filter media.
• Habitat function: Diverse native plantings support pollinator communities and serve as riparian and wetland habitat buffers where site context allows.

1.2  Vegetation Roles by Functional Type

Emergent Aquatic Vegetation — Wetlands & Wet Retention Basins

Emergent species such as softstem bulrush (Schoenoplectus tabernaemontani), cattail (Typha spp.), and blue flag iris (Iris versicolor) are suited to the permanent pool zone of wet retention basins and constructed wetlands. Their performance roles include nitrogen and phosphorus uptake, root-zone support for denitrifying bacteria, and velocity reduction and sediment settling in shallow forebay areas.

Upland and Prairie Species — Bioretention, Grass Swales, Buffers

Native grasses and forbs — including switchgrass (Panicum virgatum), little bluestem (Schizachyrium scoparium), and black-eyed Susan (Rudbeckia hirta) — are preferred for bioretention surfaces and side slopes. These species maintain open, structured soil profiles through deep root networks; tolerate the inundation/drought cycles characteristic of bioretention hydrology; and require minimal long-term inputs once established.

Shade Trees and Wooded Buffers

Canopy trees adjacent to BMPs provide ET capacity and temperature buffering for receiving waters. Both editions caution against planting species with aggressive root systems — willows, silver maples — directly within BMP filter or aggregate zones, as roots can displace engineered media and clog underdrain systems.

1.3  2023 vs. 2026 Vegetation Requirements

The 2026 edition introduces a formal 2-year vegetation establishment performance period and quantitative success thresholds — the most significant Chapter 7 change:

The 2026 Chapter 7 also provides zone-specific planting lists for bioretention cells, separating species by ponding zone, surface mulch zone, and side slope — replacing the single consolidated list used in the 2023 edition. This improves species selection accuracy and reduces mismatches between plant tolerances and actual BMP hydrologic conditions.

Establishment Performance Milestones (2026)

Section 2 — Chapter 8

Routine BMP Maintenance

2.1  Inspection Frequency

Chapter 8 ties inspection frequency to storm event magnitude and the vegetation establishment lifecycle. Inspections are required at three scales:

• Post-storm inspection: Required following any storm event producing ≥2 inches of rainfall. Scope: inlet/outlet debris, evidence of clogging, structural damage, surface ponding duration beyond design.
• Monthly inspections (establishment period): Required during the vegetation establishment period for all vegetation-dependent BMPs — bioretention, constructed wetlands, grass swales. Documents plant health, erosion, invasive colonization, mulch condition.
• Annual comprehensive inspection: Covers all system components: inlet and outlet structures, overflow spillway, vegetation condition, sediment accumulation, underdrain function (where applicable), slope stability, and maintenance record review.

Inspection records must be maintained by the BMP owner and made available to NJDEP or the approving authority upon request. The 2026 edition upgrades maintenance recordkeeping from "recommended" to required as a permit compliance obligation (see §4).

2.2  Maintenance Task Schedule

2.3  Invasive Species and Weed Control

Both editions require removal of invasive species as part of routine maintenance. Manual or mechanical removal is preferred over chemical treatment within the BMP ponding or filter zone. If herbicide is required for invasive management (e.g., Japanese knotweed, Phragmites), the product must be:

1. Approved for use in or near water environments
2. Applied by a licensed New Jersey pesticide applicator
3. Documented in the maintenance log with product name, rate, application date, and contractor name

Section 3 — Chapter 8

Retrofit and Long-Term Management

3.1  Retrofit Categories

3.2  Common Long-Term Maintenance Challenges

Media Clogging and Surface Sealing

The most common long-term failure mode for bioretention and infiltration-based BMPs. Progressive fine sediment accumulation fills pore spaces in filter media, reducing surface infiltration rates to below-design levels. Both editions prioritize prevention through adequately sized forebays and regular cleanout over corrective media replacement. When media replacement is required, the entire filter media layer must be removed and replaced with fresh-specification material — partial replacement is not effective in restoring system performance.

Vegetation Establishment Failure

Common causes include inappropriate species selection for the BMP's hydrologic regime, inadequate soil preparation or media composition, animal browsing or physical disturbance in the first growing season, and drought or extended ponding during establishment. Both editions recommend the 2-year monitoring period described in Chapter 7; the 2026 edition formalizes success thresholds and corrective triggers.

Sediment Hot Loading

BMPs receiving runoff from active construction sites or high-disturbance land uses may fill forebays within 1 to 3 years — far below design life. Both editions require that construction-phase erosion and sediment controls remain in operation until the contributing drainage area is fully stabilized, and that as-built survey data be collected at final stabilization to establish the baseline sediment depth reference for future inspections.

Section 4

Key Updates Between the 2023 and 2026 Manuals

4.1  Implications for Maintenance Planning

Maintenance Agreements Must Reference 2026 Standards

New BMP installations approved under 2026 standards require maintenance agreements that reference 2026 Chapter 8 inspection frequencies, sediment cleanout triggers, and vegetation performance thresholds. Agreements drafted under 2023 guidance should be reviewed and updated. The maintenance log is now a permit compliance record — its absence creates regulatory exposure independent of the BMP's physical condition.

Establishment Monitoring Adds a Near-Term Post-Construction Obligation

The 2026 vegetation establishment monitoring requirement adds two years of active monitoring and potential corrective actions (replanting, invasive management) that were not previously formalized. Project owners and maintenance entities should budget for six-month interval site visits, photographic documentation, and cover estimation assessments through the 24-month post-planting milestone.

GI Retrofit Path Opens Compliance Options for Existing Sites

The 2026 Chapter 8 GI retrofit guidance provides a defined compliance path for property owners with aging Non-GI stormwater infrastructure. This is particularly relevant for redevelopment projects where existing stormwater infrastructure must be brought into compliance. The retrofit-to-GI path requires on-site soil investigation per Chapter 6 (2026 protocol) and design documentation consistent with the 2026 GI BMP definition before the converted system can be credited toward the volumetric reduction standard.